Stereo speaker system

ABSTRACT

A speaker system having an array of speakers and a sealed enclosure, the number of speakers in the array being a multiple of six and the arrangement of the array being such that there is a multiple of three equally spaced speakers in each row and a multiple of two equally spaced rows. The center-to-center distance between adjacent rows is a function of the diameter of the speaker. The speakers in adjacent rows are not arranged in a rectangular array but in a parallelogram array and the angle between the centerline through speakers in one row and the center of the most closely adjacent speaker in the next row being between 30* and 60*. If two such speaker systems are connected in a stereo system, they are arranged so that the placement of the speakers in one enclosure is a mirror image of the placement of the speakers in the other enclosure.

Jan. 25, 1972 United States Patent Raichel et al.

Primary Examiner-Stephen J. Tomsky Attorney-Donald P. Gillettelnventors: Daniel Ralchel, Wyckofi; Chris G. De Vries, Jersey City, bothof NJ.

[54] STEREO SPEAKER SYSTEM [57] ABSTRACT A speaker system having anarray of speakers and a sealed en- [73] Assignee: Dathar Corporation,Paterson, NJ.

Filed: Apr. 19, 1971 [211 App]. No.: 135,126

closure, the number of speakers in the array being a multiple of six andthe arrangement of the array being such that there is a multiple ofthree equally spaced speakers in each row and a multiple of two equallyspaced rows. The center-to-center B distance between adjacent rows is afunction of the diameter mGmk 13/00, H04r 1/28 of the speaker. Thespeakers in adjacent rows are not arranged Isl/31 B in a rectangulararray but in a parallelogram array and the angle between the centerlinethrough speakers in one row and [51 Int.Cl............... 1

References Cited the center of the most closely ad acent speaker in thenext row and 60 If two such speaker systems are being between 30 SW m Nm T Am P m E" L n no D E 2 Wm .H 0 6 2 0 2 i 3 65 k y oa mm f m o et 3mmn .m m e te ee mum ollf 00.0

3,026,957 3/1962 Gladstone.. '...l81/3l B 3,273,662 9/1966 ...l8l/3l B3,275,758 9/1966 ...l8l/31B X 9 Claims, 5 Drawing Figures Roberts......

Bryan et al.

STEREO SPEAKER SYSTEM FIELD OF THEINVENTION This invention relates tothe speaker system having a multiplicity of speakers in a completelyairtight enclosure and particularly to coaxial speakers angularlyoriented and pneumatically and electrically connected in a parallelogramarray within an airtight enclosure.

BACKGROUND OF THE INVENTION The majority of stereo speakers availabletoday utilize the same configuration, i.e., the use of a large wooferfor low frequencies, one or two midrange frequency speakers, and atweeter for high frequencies. Utilization of those speakers is achievedthrough the use of electrical crossover networks.

The fidelity obtained is proportional to the quality of the speakersused.

An infrequently used arrangement of speakers within an enclosureutilizes identical speakers rectilinearly arranged in straight linesvertically and horizontally within a single enclosure. This arrangementis called an array. Heretofore, an array was unsatisfactory forultrahi-fidelity because of a lack of adequate frequency response,particularly at the lower range.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the presentinvention speakers, or, more properly, drivers, are arranged in acompletely airtight enclosure in an array consisting of T=MXN where T isthe total number of drivers and is a multiple of 6 and M is the numberof drivers per row and is a multiple of 3 and N is equal to the numberof rows and is a multiple of 2. The center of the drivers are not spacedaccording to a square or rectangular arrangement but according to aparallelogram in which the acute angle is between 30 and 60 and thespacing X between the centers of adjacent rows of the drivers is givenby the formula X=l .25D- -D/ where D is the speaker mounting diameter.

Low-frequency response errors are algebraically summed by a pneumaticcoupling of multiple drivers through an acoustic resistance. Because theerror of any one driver tends to be different from the error of theother drivers in the array, the total error is reduced. The interior ofthe speaker enclosure is loaded with fiber glass, and the acousticresistance and the fiber glass loading cause the pneumatic coupling todecrease with increasing frequency, thereby increasing the rear loadingon the speakers in the midfrequency range.

A broad direct-radiating source is also achieved because of a tightforward-radiating pattern. A higher apparent efficiency results from aninverse of the radiating loss of this quasicolumn pattern. Because ofthe small angle and time/phase relationship differences of soundarriving from one array, a listener will be unable to distinguishspeakers in the array.

The speaker system of this invention is preferably used in pairs forstereo reproduction and the arrangement of the drivers in the twoenclosures of a pair has a mirror image relationship.

It is one of the main objects of the present invention to 'provide aspeaker system, particularly for stereo use, that has an improvedresponse and forms a broad direct radiating source. Other objects willbecome apparent from the following specification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE INVENTIONThe speaker 11 in FIG. 1 includes an airtight enclosure made up of twosides 12, a top 13, a front 14, and a back and bottom which are notshown. In the front panel 14 are six individual dual-cone drivers 16-21.The driver 16 has a cone 23 and a central dust cap 24. At theperimeterof the cone 23 is a mounting ring 26 attached to the front surface ofthe panel 14. All of the other speakers 17-21 are similar to the driver16.

In accordance with this invention, six is the minimum number of driversthat can be used, and they are arranged in two vertical rows, one ofwhich consists of the drivers 16, 18, and 20 and the other, of thedrivers 17, 19, and 21. The drivers in each row are equally spaced apartand the centers of the drivers in the two rows are spaced apart by adistance X, which is an important dimension in achieving the acousticalproperties of the invention. If it is desired to use more than sixdrivers, they should be in multiples of six and should be arranged sothat there are multiples of two rows and multiples of three drivers ineach row. Thus the next size speaker system must be 24 drivers arrangedin four rows of six drivers each in order to preserve the uniqueradiation pattern.

A grille cloth 28 of special characteristics is made a part of theenclosure 11 and normally covers the drivers 16-21. Most of it has beencut away in FIG. 1 so that the drivers will be visible. The weave of thecloth should be approximately 301-5 percent porous, which is less thanthe usual grille cloth that is about 50 to percent porous. In addition,the cloth 28 must be taut enough so that no wrinkles appear in it, andthe material must not move easily in response to a slight touch. Theactual tautness should be such that a pressure of 30 grams at the centerof 1 square meter of the stretched material will cause deflection ofabout 1 mm.

When the grille cloth is applied to the speaker system 11 in thismanner, it acts as a diaphragm to the upper midrange frequencies andproduces acoustic loading to the low range of frequencies. At very highfrequencies it acts as a diffractor and absorber. The perpendiculardistance between the grille cloth 28 and each of the dust caps 24 mustbe greater than approximately 2 inches in order to achieve the properdifiractive effect of the sound.

Each of the six drivers 16-21 is a full range unit. They are closelyspaced in the airtight enclosure 11 which is characterized by wallshaving a very'high modulus of stiffness so that no rattling will occurand so that the enclosure will not act as a radiating source, and thereis relatively high acoustic coupling which causes the resonant frequencyof each driver to be different from that of every other one. This is inaddition to normal resonant differences stemming from manufacturingtolerances and is akin to the principle of staggered tuned circuits in abroadband amplifier. In the present invention, the resonance of theindividual drivers becomes inaudible and the overall response spectrumassumes a smoother contour.

The spacing X is a function of speaker size and is defined by thefollowing equation:

X=l .25 D'fiD/ZO where D is the speaker mounting diameter. In oneoperative embodiment of the invention, six 5-inch drivers were used in acabinet having a height of about 25 inches, a width of about 14 inches,and a depth of about I056 inches.

The three drivers 16, 18, and 20 in one row are not set directlyopposite the three drivers 17, 19, and 21 in the other row but areoffset slightly to form a parallelogram array. The angle 6, which is thecomplement of the acute angle of the parallelogram, is another importantparameter of the present invention. It can range from approximately 30to approximately 60 and in the aforementioned embodiment the angle was45. The angle actually used depends on the radiative dispersion of thespeakers and increases with increasing dispersion. The relationshipbetween the dispersive angle (1) and the angle 0 is given by theequation:

' 2/F /0 where both 4 and 0 are measured in degrees. The aforementionedsystem in which the speakers were displaced at an angle g of about 45?had speakers with dispersive angles of approximately 30.

The dual-cone drivers should be such that the ratio of the low-frequencycone diameter to the dust cap diameter is greater than about 8: 1. Thus,a driver having an outer diameter of 8 inches should have a dust cap of1 inch or less.

It is difficult to measure precisely the efficiency with which thesystem of the present invention transforms electrical energy intoacoustical energy, but it is of the order of 6 percent, which is greaterthan the normal 3 percent for the so-called bookcase speakers ofapproximately the same size.

FIG. 2 is a cross-sectional view of part of the enclosure 11 in FIG. 1and shows the way that the driver 16 is mountedin a well 29 in the frontpanel 14. The mounting ring 26 of the driver 16 is attached to the frontsurface of the panel 14, and the driver has its operating magneticcomponents 31 extending from the rear surface of the panel 14. Theinterior ,of the enclosure 11 is filled with sound-absorbing material32, such as fiber glass. An important aspect of the invention is theprovision of an annular collar 33 of sound-absorbing material thatsurrounds the mounting elements of the driver 16 and fills the well 29.The material of which the collar 33 is made may also be fiber glass soformed as to maintain a relatively fixed shape with a cross section thatjust fills the well 29 and does not make contact with the cone 23 of thedriver 16. This permits regular fiber glass batting 32 to be appliedover the driver without missing any voids and without fear of having anyof the absorbing material contact the cone 23 of the driver 16 or thecones of any of the other drivers.

FIG. 3 shows the electrical connection of the drivers 16-21 in FIG. 1.With this type of series-parallel connection, the total impedancebetween the input terminals 34 and 36 may be maintained at a reasonablevalue. In the aforementioned embodiment it was found that the speakersystem would handle 120 RMS watts per channel or 240 watts for a stereosystem while keeping the impedance at a nominal 8 ohms at 400 Hz. Nocrossover network was required.

FIG. 4 shows two of the speaker systems with enclosures 11 and 37arranged for stereophonic reproduction. A stereo amplifier 38 suppliespower by way of connections 39 and 40 to the enclosures l1 and 37respectively. The actual connections are made at connectors 42 and 43 inthe rear comer of the enclosures 11 and 37 respectively. In order tomaintain the proper acoustical characteristics of the system theparallelogram arrays of drivers in the enclosures 11 and 37 are suchthat the acute angles of each of the arrays are at the outer, uppercomer and the lower, inner corner of each enclosure.

FIG. shows that the same relative parallelogram arrays are maintainedwhen the enclosures l1 and 37 are placed on their sides in the usualbookcase arrangement. However, in order to maintain this relationship inwhich the outer upper corner has the acute angle of the parallelogram,the enclosures 11 and 37 must be reversed in connection to the stereoamplifier 38. Doing so makes it possible to maintain a broaddistribution of the sound, and the effective source is nearlyellipsoidal owing to the array effect. This amounts to cutting a large,more-orless diamond-shaped hole in a wall behind which the sound is Igenerated instead of cutting the usual small circle characteristic ofpreviously existing speaker systems. Thus, the apparent sound comes froma broader source and the waves reaching the listener have an apparentlarger radius of curvature than is true in the usual speaker system.

What is claimed is: 1. A speaker system comprising: A. An airtightenclosure comprising a panel; and B. A multiple of six drivers mountedon said panel and arranged in a multiple of two rows with a multiple ofthree drivers in each of said rows, the drivers in each of said rowsbeing equally spaced and said rows being parallel to each other, saiddrivers being arranged in a parallelogram array with the acute angles ofsaid parallelogram being between 30 and 60. 2. The speaker system ofclaim 1 in WhlCh each of sand drivers has a dual cone comprising anouter cone and a dust cap, and the ratio of the diameter of said outercone to said dust cap is at least approximately 8: l

3. The speaker system of claim 1 in which said panel comprises aplurality of wells, one for each of said drivers, and each of saiddrivers comprises a mounting ring attached to the external surface ofsaid panel with the remainder of each of said drivers extending throughsaid well into the interior of said enclosure.

4. The speaker system of claim 3 comprising, in addition, an annularcollar of sound-absorbent material within each of said wells andsurrounding each of said drivers but separated from the cones of saiddrivers.

5. The speaker system of claim 4 in which the interior of said enclosureis substantially filled with sound-absorbent material.

6. The speaker system of claim 1 in which all of said drivers aresubstantially identical.

7. The speaker system of claim 1 in which said rows are spaced apart bya distance X determined by the equation X=l .25DiD/20 where D is thespeaker mounting diameter.

, 8. The speaker system of claim 1 in which said acute angle is thecomplement of an angle 6 determined by the equation 2/=3/0 where 4: isthe dispersive angle of said drivers.

9. The speaker system of claim 1 comprising, in addition,

A. A second airtight enclosure comprising a panel; and

B. A multiple of six drivers mounted on said last-named panel andarranged in a multiple of two parallel rows with a multiple of threeequally spaced drivers in each of said rows, said drivers being arrangedin a parallelogram array with the acute angles of said last-named arraybeing between 30 and 60", said second enclosure facing in the samedirection as said first-named enclosure and laterally spaced therefromand with the respective acute angles of the arrays in each of saidenclosures being at the upper, outer comers of the respective panels.

1. A speaker system comprising: A. An airtight enclosure comprising a panel; and B. A multiple of six drivers mounted on said panel and arranged in a multiple of two rows with a multiple of three drivers in each of said rows, the drivers in each of said rows being equally spaced and said rows being parallel to each other, said drivers being arranged in a parallelogram array with the acute angles of said parallelogram being between 30* and 60*.
 2. The speaker system of claim 1 in which each of said drivers has a dual cone comprising an outer cone and a dust cap, and the ratio of the diameter of said outer cone to said dust cap is at least approximately 8:1.
 3. The speaker system of claim 1 in which said panel comprises a plurality of wells, one for each of said drivers, and each of said drivers comprises a mounting ring attached to the external surface of said panel with the remainder of each of said drivers extending through said well into the interior of said enclosure.
 4. The speaker system of claim 3 comprising, in addition, an annular collar of sound-absorbent material within each of said wells and surrounding each of said drivers but separated from the cones of said drivers.
 5. The speaker system of claim 4 in which the interior of said enclosure is substantially filled with sound-absorbent material.
 6. The speaker system of claim 1 in which all of said drivers are substantially identical.
 7. The speaker system of claim 1 in which said rows are spaced apart by a distance X determined by the equation X 1.25D + or -D/20 where D is the speaker mounting diameter.
 8. The speaker system of claim 1 in which said acute angle is the complement of an angle theta determined by the equation 2/ phi 3/ theta where phi is the dispersive angle of said drivers.
 9. The speaker system of claim 1 comprising, in addition, A. A second airtight enclosure comprising a panel; and B. A multiple of six drivers mounted on said last-named panel and arranged in a multiple of two parallel rows with a multiple of three equally spaced drivers in each of said rows, said drivers being arranged in a parallelogram array with the acute angles of said last-named array being between 30* and 60*, said second enclosure facing in the same direction as said first-named enclosure and laterally spaced therefrom and with the respective acute angles of the arrays in each of said enclosures being at the upper, outer corners of the respective panels. 